What is 40% of 15? 6 40% of 15 Copy 40% of 15 = 6. Formula UsedResult = (40 ÷ 100) × 15 = 6 Frequently Asked Questions What is 40% of 15?6. (40 ÷ 100) × 15 = 6.How to calculate 40%?Multiply by 0.4 (or multiply by 40 then divide by 100).